Research on dynamic vibration of transformer cores under wireless power transfer system load

With the wireless power transfer (WPT) upgrade and improve, WPT systems will be widely the load of transformers. When a transformer is connected to a WPT system, the vibration noise from the transformer core will increase because of the harmonics generated by the load. In the field of transformers with multistep-lap cores, magneto-elastic vibration is mainly caused by magnetostriction. It is feasible to continue to ensure the low no-load loss by optimizing the design and improving the manufacturing technology. However, reducing the noise from transformer cores, especially under high power WPT system load, is crucial to maintaining a high quality living environment. Harmonic components in the load-current have a larger impact to the increase of the load noise level of transformers than might be expected from their amplitude. Although previous researchers [1] have investigated the magnetic properties of noise and magnetostriction of transformer cores and much research has been devoted to the method of vibration signal analysis for monitoring power transformers [2], the core vibration at different positions with load containing harmonics has not been explicitly addressed. This research concentrated on the vibration at different positions on the core surface to identify the influence of WPT system on the vibration between the vibration amplitude and frequency. A vibration testing platform of a transformer core was produced and the transformer connected with a adjustable power WPT system in the laboratory. The vibration of the cores was measured at positions with different power level of WPT. This paper mainly focused on monitoring core vibration and frequency distribution to find suitable methods to reduce the core noise under load. These methods help predict noise levels of transformers under WPT system load.